NIAGARA GROUP. 



121 



times destroyed, leaving only these thin lamina;, as in the figure below. In other instances these 

 laminae are of a different color, and give a very pretty aspect to a polished surface. 



It is often entirely replaced by anhydrous gypsum, or by selenite, and the structure is 

 sometimes traceable in the crystallized mass of the former mineral. The large masses of 

 anhydrite at Lockport usually, if not always, fill spaces previously occupied by this coral. 



Fig. 1 a. A vertical section of a solid spheroidal mass, showing its columnar character, and the 



lines indicating stages of growth. 

 Fig. 1 h. The base of a smaller solid specimen, showing the coral surrounding, and the columns 



diverging from a stem of the Syringopora multicaulis. 

 Fig. 1 c. A vertical section, with the cells open, showing the internal character. 

 Fig. 1 eZ. A portion enlarged, showing the arrangement of the spiniform rays between the septa. 

 Fig. 1 e. A similar section where the rays are nearly obsolete. 

 Fig. 1 /. A section enlarged, showing the surface of the walls of the cell, where the ray.s are 



broken off. 

 Fig. 1 g. A single space between two septa, greatly enlarged. 

 Fig. \ h. A. transverse section of the cells parallel to the surface. 

 Fig. 1 i. The same enlarged. 



Position and locality. Throughout the Niagara limestone : abundant at Lockport, and less 

 common at Rochester and other places. (State CoUeetwn.) 



AstTocerium Tennstnm. 



The concentric lamins, indicating stagea of growth, are alone preserved. 



[ Paljeontologv — Vol. n.] 



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